1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly to a method of updating system information in a wireless communication system.
2. Discussion of the Related Art
System Information (SI) includes various pieces of information about a radio environment, such as code information and a power level used in a current cell or neighbor cells. A user equipment (UE) has to receive system information about a new BS when the UE is first registered to a BS system or performs handover to a new BS. The UE can know the state of the BS using the system information and can know a method and procedure of accessing the BS when accessing the BS.
When the Radio Resource Control (RRC) layer of a specific UE is connected to the RRC layer of a BS so that they can exchange RRC messages, it is said that the corresponding UE is in the RRC-connected state. When they are not connected to each other, it is said that the corresponding UE is in the idle state. When a UE is in the idle state and switched to the RRC-connected state, the UE attempts access using an access method based on system information acquired by a BS.
A BS can update some or all pieces of system information, when necessary. Before applying updated system information to a system, the BS first informs a UE whether system information has been updated so that the UE is prepared to receive the updated system information.
In conventional arts, since updated system information is transmitted only once, there is a problem that UEs failing to receive radio frames in which the updated system information is transmitted are unable to access a system until the UEs receive the updated system information. The typical transmission period of system information is set to a relatively long time. Accordingly, a communication recovery time during which the UEs receive the newly transmitted system information is also delayed. This becomes a factor to deteriorate the service quality of UEs. Accordingly, there is a need for a more reliable method of updating system information.